Mono bore riser adapter

ABSTRACT

A riser adapter system for coupling a mono-bore riser to a dual bore subsea wellhead assembly with a main bore and an annulus bore, includes an upper adapter with an upper bore offset from a radially centered point of a downward facing face of the upper adapter. The upper bore is in fluid communication with a riser bore of the mono-bore riser. A lower adapter has a first end selectively mated to the downward facing face of the upper adapter and an opposite facing second end. The lower adapter has a lower bore offset from a central axis of the lower adapter. The downward facing face of the upper adapter and the second end of the lower adapter are alternately mated to the subset wellhead assembly so that the riser bore is alternately in fluid communication with the main bore and the annulus bore of the subsea wellhead assembly.

BACKGROUND

1. Field of Invention

This invention relates in general to offshore drilling and production equipment and in particular to workover operations with a dual bore tree coupled to a single bore riser.

2. Description of Related Art

Offshore hydrocarbon exploration and production activities typically include subsea assemblies for transporting oil, gas, and other produced matter, as well as well injection materials. The subsea assembly is usually located at the well on the seabed and connected to a fixed or floating structure or platform by means of a conduit, such as a riser, between the subsea assembly and the platform. The subsea assembly often includes a wellhead or other type of equipment positioned on the seabed or in a fixed position above the seabed. The subsea assembly can include either a mono-bore or dual bore subsea tree.

The riser can be a mono-bore type riser or a dual bore type riser. A dual bore riser comprises a production or main pipe and an annulus pipe extending in parallel with the production pipe. A mono-bore riser comprises a production pipe but no annnlus pipe. Generally, a mono-bore riser is safer and easier to handle than a dual bore riser. Furthermore, the costs associated with the manufacturing and use of a mono-bore riser are substantially lower as compared to a dual bore riser. Thus, the use of a mono-bore riser has advantages, even when the subsea assembly has a dual bore, and particularly when the riser is to be used at great sea depths.

When a mono-bore riser is secured to a dual bore subsea assembly, it is sometimes desirable to be able to run both a production plug through the mono-bore riser and into the main bore of the subsea assembly, and an annulus plug through the mono-bore riser and into the annulus bore of the subsea assembly. When running an annulus plug, an angle between the bore of the mono-bore riser and the bore of the annulus pipe, or an angle of the flow path between the bore of the mono-bore riser and the bore of the annulus bore, of even one degree can prevent the efficient installation of the annulus plug.

SUMMARY OF THE DISCLOSURE

The methods and systems of the current disclosure provide an adapter that allows a single or mono-bore riser to be used with a dual bore tree. The mono-bore riser can selectively communicate with either the full or main bore or the annulus bore of the dual bore tree without having an angular path along the bore of the mono-bore riser, the main bore or the annulus bore.

In an embodiment of this disclosure, a riser adapter system for coupling a mono-bore riser to a dual bore subsea wellhead assembly with a main bore and an annulus bore includes an upper adapter with an upper bore offset from a center point of a downward facing face of the upper adapter. The upper bore is in fluid communication with a riser bore of the mono-bore riser. A lower adapter has a first end selectively mated to the downward facing face of the upper adapter and an opposite facing second end. The lower adapter has a lower bore offset from a central axis of the lower adapter. The downward facing face of the upper adapter and the second end of the lower adapter are alternately mated to the subsea wellhead assembly so that the riser bore is alternately in fluid communication with the main bore and the annulus bore of the subsea wellhead assembly.

In another embodiment of the current disclosure, a riser adapter system for coupling a mono-bore riser to a dual bore subsea wellhead assembly with a main bore and an annulus bore, includes a stress joint secured to an end of the mono-bore riser. The stress joint has an upper bore aligned with a riser bore of the mono-bore riser and offset from a center point of a downward facing face of the stress joint. A lower adapter is alternately located on a side wing of the subsea wellhead assembly and engaged with the downward facing face of the stress joint. The lower adapter has a lower bore offset from a central axis of the lower adapter. The riser bore is alternately in fluid communication with the main bore through the upper bore and in fluid communication with the annulus bore through the upper bore and the lower bore.

In yet another embodiment of the current disclosure, a method for coupling a mono-bore riser to a dual bore subsea wellhead assembly with a main bore and an annulus bore includes securing an upper adapter to the mono-bore riser so that a riser bore of the mono-bore riser is in fluid communication with an upper bore of the upper adapter. The upper adapter is secured to the subsea wellhead assembly so that the riser bore is in fluid communication with the main bore. The upper adapter is lifted off of the subsea wellhead assembly and rotated 180 degrees. The upper adapter is lowered onto a lower adapter, the lower adapter having a lower bore. The lower adapter is secured to the subsea wellhead assembly so that the riser bore is in fluid communication with the annulus bore.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the features, advantages and objects of the invention, as well as others which will become apparent, are attained and can be understood in more detail, more particular description of the invention briefly summarized above may be had by reference to the embodiment thereof which is illustrated in the appended drawings, which drawings form a part of this specification. It is to be noted, however, that the drawings illustrate only a preferred embodiment of the invention and is therefore not to be considered limiting of its scope as the invention may admit to other equally effective embodiments.

FIG. 1 is a schematic elevation view of a subsea wellhead assembly with a riser adapter system of an embodiment of this disclosure.

FIG. 2 is a schematic section view of the riser adapter system of FIG. 1, shown with the bore of the upper adapter registering with the main bore.

FIG. 3 is a schematic section view of the riser adapter system of FIG. 1, shown with the upper adapter located over the lower adapter on the wellhead assembly side wing.

FIG. 4 is a schematic section view of the riser adapter system of FIG. 1 shown with the bore of the upper adapter and the lower adapter registering with the annulus bore.

DETAILED DESCRIPTION OF THE DISCLOSURE

The methods and systems of the present disclosure will now be described more fully hereafter with reference to the accompanying drawings in which embodiments are shown. The methods and systems of the present disclosure may be in many different forms and should not be construed as limited to the illustrated embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey its scope to those skilled in the art. Like numbers refer to like elements throughout.

It is to be further understood that the scope of the present disclosure is not limited to the exact details of construction, operation, exact materials, or embodiments shown and described, as modifications and equivalents will be apparent to one skilled in the art. In the drawings and specification, there have been disclosed illustrative embodiments and, although specific terms are employed, they are used in a generic and descriptive sense only and not for the purpose of limitation.

Referring to FIG. 1, a schematic view of an example of a subsea wellhead assembly 10 is shown mounted on a wellhead 12 over a subsea well 14 used for hydrocarbon production activities. In the example of FIG. 1, the subsea wellhead assembly 10 is a subsea intervention system located above the sea floor that includes a dual bore subsea tree 16 located above wellhead 12. Subsea tree 16 can have an annulus bore 18 for well servicing. Tree 16 can also have a main bore 20 for providing a fluid path into and out of well 14 for producing hydrocarbons to the water's surface. Subsea tree 16 can be used to monitor and control fluids flowing into and out of well 14.

Above subsea tree 16 is well control package or lower riser package 22. Lower riser package 22 can be used to provide a barrier to contain well fluids during a well intervention, during a disconnection of upper system components from the subsea wellhead assembly 10, or in the case of an emergency, to prevent the spill of such fluids into the environment. A lower end of lower riser package 22 is secured to subsea tree 16 and an upper end of lower riser package 22 can be connected to an emergency disconnect package 24.

Emergency disconnect package 24 can provide riser containment during a normal riser disconnection operation or in an emergency quick disconnect so that fluids within mono-bore riser 26 do not spill into the environment. A quick release connector (not shown) can be located between lower riser package 22 and emergency disconnect package 24 to accommodate the connection and disconnection between lower riser package 22 and emergency disconnect package 24. Emergency disconnect package 24 can also include a control module to assist in the management of well intervention and workover operations. Annulus bore 18 and main bore 20 extend from subsea tree 16, through lower riser package 22, through emergency disconnect package 24, and open on an upper end of emergency disconnect package 24.

Looking now at FIGS. 1-4, between emergency disconnect package 24 and mono-bore riser 26 is stress joint or upper adapter 28. Mono-bore riser 26 can be supported in tension by a surface structure, such as a fixed or floating platform (not shown). Mono-bore riser 26 is subject to ocean currents, wave motion and other external forces and stresses as it is suspended from the surface structure, that may create large bending stresses in mono-bore riser 26. The connection between mono-bore riser 26 and emergency disconnect package 24 can be susceptible to failure due to the stresses on such connection cause by these external forces. Upper adapter 28 can be shaped to resist failure of the connection between mono-bore riser 26 and emergency disconnect package 24, by having a taper in cross section to transmit the stresses over the length of the stress joint, rather than having the stresses localized at a shorter connector length or at a single location. In the example embodiments of FIGS. 1-4, upper adapter 28 has a partial triangular cross section, flaring outward over half of the diameter so that upper adapter 28 is radially wider closer to a bottom end adjacent emergency disconnect package 24 than a top end which is adjacent mono-bore riser 26.

Riser adapter system 30 can be used to couple mono-bore riser 26 to subsea wellhead assembly 10. Riser adapter system 30 includes stress joint or upper adapter 28. Upper adapter 28 includes upper bore 32 which extends from downward facing face 34 to an opposite face 36 of upper adapter 28. Upper bore 32 has an upper bore axis 35 and is offset from a radially centered point 38 of downward facing face 34 of upper adapter 28. Opposite face 36 of upper adapter 28 engages mono-bore riser 26 and upper bore 32 is in fluid communication with riser bore 40 of mono-bore riser 26.

Looking at FIG. 2, opposite face 36 can mate with an upward facing surface 41 of subsea wellhead assembly 10 and upper bore 32 can register with, and be in fluid communication with, main bore 20 of subsea wellhead assembly 10. Upper bore 32 can have a diameter generally equal to the diameter of main bore 20 of subsea wellhead assembly 10. When upper bore 32 of upper adapter 28 registers with main bore 20, downward facing face 34 of upper adapter 28 seals across annulus bore 18, blocking access to annulus bore 18 from the upward facing surface 41 of subsea wellhead assembly 10. In one example, when upper bore 32 of upper adapter 28 registers with main bore 20, a flow path from riser bore 40, through upper adapter 28, and to main bore 20, is free of an angle. That is, riser bore 40, upper bore 32 and main bore 20 are each centered around upper bore axis 35, which is a single straight line. Having a flow path from riser bore 40, through upper adapter 28, and to main bore 20, that is free of an angle will allow for a tubing hanger or production plug to be efficiently run into, or removed from, main bore 20.

Subsea wellhead assembly 10 can include a side bore 43 that is is fluid communication with annulus bore 18. Side bore 43 can extend from annulus bore 18, through subsea wellhead assembly 10, and out of subsea wellhead assembly 10 at a surface other than upward facing surface 41. An annulus valve can control the flow of fluids through side bore 43 and an umbilical hose or other tubular member can be used to provide a fluid flow path between side bore 43 and a fluid source or fluid receptacle located, as an example, at the surface structure. Because the side bore 43 meets annulus bore 18 at a location below upward facing surface 41 of subsea wellhead assembly 10, fluids can circumvent the riser adapter system 30 and enter or exit annular bore 18 through side bore 43.

Riser adapter system 30 can also include lower adapter 42. Lower adapter 42 has a first end 44 that is upward facing and a second end 45 that is downward facing opposite first end 44. Lower adapter 42 has lower bore 46 that is radially offset from a central axis 48 of lower adapter 42. First end 44 of lower adapter 42 can be attached and detached from upper adapter 28.

Looking at FIGS. 3-4, when lower adapter 42 is attached to upper adapter 28, first end 44 of lower adapter 42 is mated with downward facing face 34 of upper adapter 28 so that lower bore 46 registers with, and is in fluid communication with, upper bore 32, and is also in fluid communication with riser bore 40 of mono-bore riser 26. When lower adapter 42 is attached to upper adapter 28, lower adapter 42 can be landed on subsea wellhead assembly 10 with (FIG. 4). In such a position, lower bore 46 registers with, and is in fluid communication with, annnlus bore 18 of subsea wellhead assembly 10. Lower bore 46 can have a lower bore axis 47 and a diameter generally equal to the diameter of annulus bore 18. When lower bore 46 of lower adaptor 42 registers with annulus bore 18, second end 45 of lower adapter 42 seals across main bore 20. In such a configuration, access to main bore 20 is restricted at upward facing surface 4l and fluids are prevented from entering and exiting main bore 20 at upward facing surface 41. Second end 45 can engage an upward facing surface 41 of subsea wellhead assembly 10 and be secured to subsea wellhead assembly 10 with lower connector member 54.

When lower bore 46 of lower adapter 42 registers with annulus bore 18, a flow path from riser bore 40, through upper adapter 28, lower bore 46 and to main bore 20, is free of an angle. That is, riser bore 40, upper bore 32, lower bore 46 and annulus bore 18 are each centered around lower bore axis 47, which is a single straight line. Having a flow path from riser bore 40, through upper adapter 28, and to annulus bore 18, that is free of an angle will allow for an efficient procedure for running an annulus plug into annulus bore 18, or removing the annulus plug from annulus bore 18.

Turning to FIG. 3, lower adapter 42 can alternately be landed and parked on subsea wellhead assembly 10. Emergency disconnect package 24 can include side wing 50 and second end 45 of lower adapter 42 can be mated with an upward facing surface of side wing 50. In an example configuration, side wing 50 extends radially outward from emergency disconnect package 24. Side wing 50 has an upward facing surface for engaging and supporting second end 45 of lower adapter 42 when lower adapter 42 is parked on side wing 50.

Looking again at FIGS. 1-4, both upper adapter 28 and lower adapter 42 have connector members 52, 54 for securing and un-securing upper adapter 28 and lower adapter 42 to subsea wellhead assembly 10, and also for securing and un-securing upper adapter 28 to lower adopter 42, as desired. Upper adapter 28 includes upper connector member 52. Upper connector member 52 can alternately secure upper connector member 52 to subsea wellhead assembly 10 or to lower adapter 42. Lower connector member 54 can alternately secure lower adapter 42 over annulus bore 18 of subsea wellhead assembly 10 or to side wing 50 of subsea wellhead assembly 10. Connector members 52, 54 can be for example, ring shaped clamps that engage flanges of the components to be connected, or can be other known subsea member connection devices such as bolted connectors, collet connectors and other mechanical connectors. Connector members 52,54 can be operated by a remotely operated vehicle 56.

In an example of operation, looking at FIGS. 1-2, to couple mono-bore riser 26 to dual bore subsea wellhead assembly 10 with main bore 20 and annulus bore 18 includes securing upper adapter 28 to mono-bore riser 26 so that riser bore 40 of mono-bore riser 26 is in fluid communication with upper bore 32 of upper adapter 28. Upper adapter 28 can be secured to emergency disconnect package 24 of upper adapter 28 so that riser bore 40 is in fluid communication with main bore 20. Upper adapter 28 can be landed on upward facing surface 41 of subsea wellhead assembly 10. Upper adapter 28 can be secured to emergency disconnect package 24 above the surface of the water, before emergency disconnect package 24 is lowered through the ocean water to the other components of the subsea wellhead assembly 10. In this position, there is access through riser bore 40 to main bore 20 for example, the access being straight and free of an angle, for running or removing a production or tubing hanger plug or performing other operations through riser bore 40 and main bore 20. Downward facing face 34 of upper adapter 28 seals across annulus bore 18, blocking access to annuls bore 18 from the upward facing surface 41 of subsea wellhead assembly 10. Lower adapter 42 can, during this time, be parked on side wing 50 of subsea wellhead assembly 10.

Upper connector 52, which secures upper adapter 28 to subsea wellhead assembly 10, can then be un-secured and upper adapter 28 can be lifted off of subsea wellhead assembly 10 by the surface structure. Upper connector 52 can be rotated 180 degrees around a vertical axis and moved radially sideways so that upper adapter 28 aligns with lower adapter 42. Looking at FIG. 3, upper adapter 28 can be lowered onto lower adapter 42. Because upper adapter 28 has been rotated 180 degrees, upper bore 32 will align with lower bore 46. Upper bore 32 has a greater diameter than lower bore 46 and there will be a transition of bore diameters where upper bore 32 meets lower bore 46. Upper adapter 28 can be secured to lower adapter 42 with upper connector 52. In alternate embodiments, lower adapter 42 can bo positioned on side wing 50 in a way that upper bore 32 will align with lower bore 46 without first rotating upper adapter 28. Upper adapter 28 together with lower adapter 42 can then be rotated 180 degrees after being lifted as one unit off of side wing 50.

Looking at FIG. 4. upper adapter 28 together with lower adapter 42 can bellfted as one unit off of side wing 50 of subsea wellhead assembly 10. and landed on upward facing surface 41 of subsea wellhead assembly 10. In this position,, there is access through riser bore 40 to annulus bore 18, the access being straight and free of an angle for running or removing an annulus plug or performing other operations through riser bore 40 and annulus bore 18. Second ead 45 of lower adapter 42 seals across main bore 20, preventing fluids from entering and exiting main bore 20 at upward facing surface 41. A pair of ring shaped gaskets or seals, one that surrounds the opening of main bore 20, and one that surrounds the opening of annulus bore 18, can provide a sealing means between main bore 20, annulus bore 18, and the upper adapter 28 or lower adapter 42, as applicable. An alignment mechanism, such as a twin guide pin system or other alignment means known in the art, can be used to align upper adaptor 28 and lower adapter 42 with upward facing surface 41 of subsea wellhead assembly 10 so that upper bore 32 and lower bore 46, as applicable, are properly aligned with main bore 20 and annulus bore 18, respectively.

In order to gain access once again to main bore 20, lower connector can be un-secured and lower adapter 42 can be lifted off of subsea wellhead assembly 10, rotated 180 degrees and parked back on side wing 50 of subsea wellhead assembly 10. Upper adapter 28 can be secured once again to subsea wellhead assembly 10 with upper connector 52 so that riser bore 40 is in fluid communication with main bore 20 (FIGS. 1-2).

The terms “vertical”, “horizontal”, “upward”, “downward”, “above”, and “below” and similar spatial relation terminology are used herein only for convenience because elements of the current disclosure may be installed in various relative positions.

The system and method described herein, therefore, are well adapted to carry out the objects and attain the ends and advantages mentioned, as well as others inherent therein. While a presently preferred embodiment of the system and method has been given for purposes of disclosure, numerous changes exist in the details of procedures for accomplishing the desired results. These and other similar modifications will readily suggest themselves to those skilled in the art, and are intended to be encompassed within the spirit of the system and method disclosed herein and the scope of the appended claims. 

What is claimed is:
 1. A riser adapter system for coupling a mono-bore riser to a dual bore subsea wellhead assembly with a main bore and an annulus bore, the riser adapter system comprising: an upper adapter with an upper bore offset from a radially centered point of a downward facing face of the upper adapter, the upper bore being in fluid communication with a riser bore of the mono-bore riser; a lower adapter with a first end selectively mated to the downward facing face of the upper adapter and an opposite facing second end, the lower adapter having a lower bore offset from a central axis of the lower adapter; and wherein the downward facing face of the upper adapter and the second end of the lower adapter are alternately mated to the subsea wellhead assembly so that the riser bore is alternately in fluid communication with the main bore and the annulus bore of the subsea wellhead assembly.
 2. The riser adapter system according to claim 1, wherein the lower adapter is alternately located on a side wing of the subsea wellhead assembly and mated to the downward facing face of the upper adapter.
 3. The riser adapter system according to claim 1, wherein the upper bore is selectively in fluid communication with the main bore of the subsea wellhead assembly.
 4. The riser adapter system according to claim 1, wherein the lower bore is selectively in fluid communication with the annulus bore of the subsea wellhead assembly.
 5. The riser adapter system according to claim 1, wherein the upper bore has a diameter generally equal to the diameter of the main bore of the subsea wellhead assembly, and the lower bore has a diameter generally equal to the diameter of the annulus bore.
 6. The riser adapter system according to claim 1 , wherein the upper adapter includes an upper connector member alternately securing the upper adapter to the subsea wellhead assembly and the lower adapter, the upper connector member being remotely operated vehicle operable.
 7. The riser adapter system according to claim 1, wherein the lower adapter includes a lower connector member alternately securing the lower adapter over the annulus bore of the subsea wellhead assembly and to a side wing of the subsea wellhead assembly.
 8. The riser adapter system according to claim 1, wherein the subsea wellhead assembly includes an emergency disconnect package and the annulus bore extends through the emergency disconnect package, and wherein the lower adapter is alternately located on a side wing of the emergency disconnect package and in fluid communication with the annulus bore of the subsea wellhead assembly.
 9. The riser adapter system according to claim 1, wherein when the lower bore of the lower adapter registers with the annulus bore, the second end of the lower adapter seals across the main bore.
 10. A riser adapter system for coupling a mono-bore riser to a dual bore subsea wellhead assembly with a main bore and an annnlus bore, the riser adapter system comprising: a stress joint secured to an end of the mono-bore riser, the stress joint having an upper bore aligned with a riser bore of the mono-bore riser and offset from a center point of a downward facing face of the stress joint; a lower adapter alternately located on a side wing of the subsea wellhead assembly and engaged with the downward facing face of the stress joint, the lower adapter having a lower bore offset from a central axis of the lower adapter; and wherein the riser bore is alternately in fluid communication with the main bore through the upper bore and in fluid communication with the annulus bore through the upper bore and the lower bore.
 11. The riser adapter system according to claim 10, wherein when the riser bore is in fluid communication with the main bore, the downward facing face of the upper adapter seals across the annulus bore.
 12. The riser adapter system according to claim 10, wherein when the riser bore is in fluid communication with the annulus bore, an end of the lower adapter seals across the main bore.
 13. The riser adapter system according io claim 10, wherein the stress joint includes an upper connector member alternately securing the upper connector member to the subsea wellhead assembly and the lower adapter, the upper connector member being remotely operated vehicle operable.
 14. The riser adapter system according to claim 10, further alternately comprising: a flow path from the riser bore, through the stress joint, and to the main bore, that is free of an angle; and a flow path from the riser bore, through the upper bore, the lower bore, and to the annulus bore, that is free of an angle.
 15. A method for coupling a mono-bore riser to a dual bore subsea wellhead assembly with a main bore and an annulus bore, the method comprising: (a) securing an upper adapter to the mono-bore riser so that a riser bore of the mono-bore riser is in fluid communication with an upper bore of the upper adapter; (b) securing tbe upper adapter to the subsea wellhead assembly so that the riser bore is in fluid communication with the main bore; (c) lifting the upper adapter off of the subsea wellhead assembly, rotating the upper adapter 180 degrees, and lowering the upper adapter onto a lower adapter, the lower adapter having a lower bore; and (d) securing the lower adaptor to the subsea wellhead assembly so that the riser bore is in fliud communication with the annulus bore.
 16. The method according to claim 15, wherein tbe upper bore is offset from a center point of a downward facing face of the upper adapter, and wherein step (b) includes sealing across the annulus bore with the downward facing face.
 17. The method according to claim 15, wherein the lower adapter has a first end and a second end and the lower bore is offset from a from a central axis of the lower adapter, and wherein step (c) includes engaging a downward facing face of the upper adapter with the first end of the lower adapter and step (d) includes sealing across the main bore with the second end.
 18. The method according to claim 15, wherein: step (b) includes aligning the upper bore with the main bore along a central axis of the main bore, providing a flow path from the riser bore, through the upper bore, and to the main bore, that is free of an angle; and step (d) includes aligning the lower bore with the annulus bore along a central axis of the annulus bore, providing a flow path from the riser bore, through the upper bore, the lower bore, and to the annulus bore, that is free of an angle.
 19. The method according to claim 15, wherein step (c) includes lowering the upper adapter onto the lower adapter on a side wing of the subsea wellhead assembly and securing a downward facing face of the upper adapter to a first end of the lower adapter.
 20. The method according to claim 15, further comprising after step (d), lifting the lower adapter off of the subsea wellhead assembly, rotating the lower adapter 180 degrees, and lowering the lower adapter onto a side wing of the subsea wellhead assembly, then securing the upper adapter to the subsea wellhead assembly so that the riser bore is in fluid communication with the main bore. 